According to Doc 9157:
- A350-900 4E 64.7m wingspan 12.9m omgws
- A350-1000 4E 64.7m wingspan 12.8m omgws

Hence per Annex 14 3.13.6 the minimum clearance distance on aircraft stands is 7.5 m.

Most dimensions can be found here:
https://www.airbus.com/sites/g/files/jlcbta136/files/2021-11/Airbus-Com…

Thank you for the prompt answer Robert Gottwald.

We are receiving some denying to park on some stands that the 777 operates.

Do you have any additional information that could help, please?

I am not sure what you need exactly. The 777 variants in service all have narrower wingspans than the A350. Since you have to also get in and out of the stands, this could very well be. I would recommend to get in contact with the airport operator.